Lubricating oil compositions of improved thermal stability

ABSTRACT

Mineral lubricating oil compositions are prepared containing oil-soluble additives for sludge control, having improved high temperature oxidation stability and thus permitting longer periods of service before it becomes necessary to drain the used oil and replace it with fresh oil. The novel additive mixture is prepared by reacting elemental sulfur with long chain (C16 ) oilsoluble olefinically unsaturated monomeric or polymeric hydrocarbons, e.g. polyisobutylene, and using such sulfurized compounds in conjunction with conventional ashless dispersants with or without using additional ashless dispersants which have previously been reacted with elemental sulfur. Many of the hydrocarbons used as starting materials, in their unsulfurized state, have heretofore been used as viscosity index improvers in lubricating oil compositions.

United States Patent Panzer 51 May 23, 1972 [54] LUBRICATING OILCOMPOSITIONS OF IMPROVED THERMAL STABILITY [21] Appl.No.: 889,745 Y [52]US. Cl ..252/47.5, 252/45 (51] Int. Cl. ..Cl0m 1/38 [58] Field of Search..252/45, 47.5, 51.5 A

[56] References Cited UNITED STATES PATENTS 2,312,750 3/1943 Cohen..252/45 X 2,337,473 12/1943 Knowles et al.. ....252/45 X 3,172,8923/1965 Le Suer et al... ....252/5l.5 A

3,309,316 3/1967 McNinch ..252/47.5

3,352,782 11/1967 Brasch ..252/47.5 3,498,915 3/1970 Coleman ..252/45 XPrimary Examiner-Daniel E. Wyman Assistant Examiner-W. CannonAttorney-Pearlman and Stahl and Ernest V. Haines [57] ABSTRACT Minerallubricating oil compositions are prepared containing oil-solubleadditives for sludge control, having improved high temperature oxidationstability and thus permitting longer periods of service before itbecomes necessary to drain the used oil and replace it with fresh oil.The novel additive mixture is prepared by reacting elemental sulfur withlong chain (C oil-soluble olefinically unsaturated monomeric orpolymeric hydrocarbons, e.g. polyisobutylene, and using such sulfurizedcompounds in conjunction with conventional ashless dispersants with orwithout using additional ashless dispersants which have previously beenreacted with elemental sulfur. Many of the hydrocarbons used as startingmaterials, in their unsulfurized state, have heretofore been used asviscosity index improvers in lubricating oil compositions.

13 Claims, No Drawings LUBRICATING OIL COMPOSITIONS OF IMPROVED THERMALSTABILITY BACKGROUND OF THE INVENTION The present invention relates tothe use in mineral lubricating oil compositions of a combination ofoil-soluble sulfurized olefinic compounds with the so-called ashlessdispersants which are likewise oil-soluble and have been usedin'lubricating oil compositions for some years. I

Numerous addition agents have heretofore been prepared for use inautomotive mineral lubricating oils, including the so-called heavy dutyoils which are also employed in railroad diesel engines and gas engines.The prior researchers have been successful in finding various types ofoil-soluble organic compounds which exhibit specialized and specificproperties of a beneficial nature when they are incorporated into thesemineral lubricating oils. For many years now, organic compounds havebeen added in minor amounts to lubricating oils for the purpose oflowering their pour point, of improving their viscosity index, ofaffording increased resistance to oxidation, of imparting antiwearproperties, of inhibiting sludge formation and of dispersing sludge whenit is formed during use of the oils. The use of such additives at thepresent time enjoys widespread commercial acceptance. Good oxidationstability and good dispersing along with good detergency have becomeessential requirements for automotive lubricants. This is particularlyso in connection with lubricating oils used in socalled heavy dutyengines such as gas engines and railroad diesel engines. Additionally,the additives employed must necessarily be accepted from the standpointof lack of wear or attack on the specialized types of bearings employedin internal combustion engines at the present time.Copper-lead-containing bearings are unusually susceptible to wear andcorrosion problems. Suitable compounded oils must exhibit low corrosionand low bearing wear with respect to the specialized bearings which theycontact in order to be acceptable commercially.

In the past, it has been proposed to add sulfurized polyisobutylene ofrelatively low molecular weight (boiling range l75260 C.) or of highermolecular weights, or derivatives thereof, to lubricating oils. See, forexample, U.S. Pat. Nos. 2,279,688; 2,312,750; 2,330,858; 2,535,705 and2,658,900. Also, it has been proposed in the past to employ sulfurizedashless dispersants in lubricating oils, see U.S. Pat. Nos. 3,390,086and 3,309,316; whose disclosures are incorporated herein by reference.By the incorporation of elemental sulfur into a conventionally usedolefinically unsaturated hydrocarbon, namely polyisobutylene, and by theincorporation of elemental sulfur into a conventional ashlessdispersant, it was possible to increase the effectiveness of thesematerials for their intended purpose even in the case of lubricating oilcompositions being subjected to extremely high temperatures during use.The thermal stability of the lubricating oils containing a combinationof such additives, along with unsul furized ashless dispersants, wasgreatly enhanced and resulted in the expended and more diversified, useof lubricating oils than when such oils contained either of these typesof additives alone; because of the enhanced oxidation stability orresistance to oxidative degradation achieved by the introduction of theelemental sulfur into these compounds.

It has now been discovered that the use of sulfurized oil solubleolefinically unsaturated long chain hydrocarbons in conjunction with aconventional ashless dispersant (with or without the use of a sulfurizedashless dispersant) gives rise to lubricating oils which have unusuallyhigh oxidation stability at high temperatures and which exhibit aheretofore unattainable degree of resistance to sludge formation and anexcellent dispersion of the sludge that is formed. What this amounts tois that the versatility of lubricating oils as to their scope of use,where such oils contain this combination of additives, has beenincreased markedly because of the enhanced high temperaturecharacteristics achieved by so compounding these oils. Another advantagelies in the fact that even when using such compounded oils at lowertemperatures or at temperatures ordinarily encountered in the automotiveengines, the life of the oil is increased over that heretoforeattainable and so such oils may be employed for longer periods of timenecessitating fewer oil changes and longer engine running periodsbetween changes. Whereas, heretofore, a heavy diesel engine operatingunder severe high temperature conditions would require an oil changeafter 1,500 hours of operation, because of oxidation breakdown of theoil and excessive sludge buildup due to high temperature conditions in.the oil, it is now possible to increase the life of that same oil usedunder the same conditions by as much as 50 percent through the use ofthe combination of a sulfurized oil-soluble unsaturated hydrocarbon incombination with an ashless dispersant and, optionally, a sulfurizedashless dispersant.

The materials which may be treated with elemental sulfur or with sodiumpolysulfide, which is the chemical equivalent of elemental sulfur, aremany and varied in number and constitute a great many of thoseoil-soluble unsaturated polymeric aliphatic hydrocarbon compoundspossessing olefinic unsaturation which have heretofore customarily andconventionally been employed as viscosity index improvers in lubricatingoils. It has now been discovered that the introduction into theseolefinically unsaturated aliphatic hydrocarbon compounds, as well asinto similar compounds not possessing V.l. improving properties, ofelemental sulfur enhances their properties when used in lubricatingoils. The ashless dispersants, used in combination, are well-knownconventional and commercially available compounds. They may be employedin the form in which they are commercially available. They may besulfurized, i.e. subjected to a reaction with'elemental sulfur asdescribed and claimed in the aforementioned U.S. Pat. No. 3,390,086whose disclosure is incorporated hereinto by reference and used inconjunction with the conventional ashless dispersants of commerce.

Among the many varied types of olefinic unsaturated hydrocarbons whichare used as starting compounds which are to be treated with elementalsulfur or its chemical equivalent such as sodium polysulfide are:

1. long chain (C -C alpha monoolefin monomers or mixtures thereof; 2.homopolymers of C to C alpha monoolefins; 3. copolymers of C to C alphamonoolefins with different C to C alpha monoolefins; and

4. terpolymers of three different monomers of (3) or of two difierentmonomers (3) with a diolefin such as methylene norbornene or butadieneor with still a third alpha monoolefin.

Exemplary of the reactants that may be employed as starting materialsare the following: (copolymers are shown thus: monomer monomer) C alphaolefin mixtures, octadecenel, hexadecene-l, tetradecene-l, C -C alphaolefins, polypropylene, polyisobutylene, ethylene-propylene,ethylene-isobutylene, ethylenepropylene-isobutylene,ethylene-propylene-butadiene-1-3, n-octene-l isobutylene,propylene-pentene-2, ethylene-propylene-n-dodecene,ethylene-isobutylene-n-decene, ,ethylene-propylene-1,4-hexadiene,ethylene-propylene-dicyclopentadiene, ethylenepropylene-methylenenorbornene. The number average molecular weights of the polymers,copolymers, or terpolymers generally range between about 300 and about150,000, preferably between about 900 and about 70,000, and they aresoluble in lubricating oils. These polymeric products are plasticsolids, waxy or elastomeric depending on their molecular weights. Theirphysical properties and appearance are not the'criteria that determinetheir efficacy, when sulfurized, and used in lubricating oils. The morehighly amorphous (non-crystalline) products are preferred.

In general, crystalline contents of less than 25 wt. percent in thepolymers are desirable and when such polymers are sulfurized, their usein lubricating oils affords viscosity index improving properties as wellas oxidative and sludge inhibiting properties to the oils Thepolymerization reactions used to produce the polymeric hydrocarbonproducts are all well known to the art and the polymers are well-knowncommercial articles sold on the open market. The polymeric hydrocarbonsare formed by polymerizing, copolymerizing, or terpolymerizing theolefinic monomers using Friedel-Crafts type catalysts, the so-calledmetallo alkyl, or coordination catalysts, or the Ziegler type catalysts.The homopolymers, i.e. polyisobutylene, most generally are produced byusing Friedel-Crafts type catalysts such as boron trifluoride oraluminum chloride at low temperatures. Representative U.S. Pats.disclosing such products and their methods of preparation are Nos.2,239,501; 2,534,095; 2,781,410; and 2,825,721 whose disclosures areincorporated herein by reference. The copolymers and terpolymers areusually produced by the use of coordination of metallo alkyl typecatalysts. Representative U.S. Pats. disclosing suitable startingmaterials of these types, which may be sulfurized, are: Nos. 2,691,647;2,975,159; 2,933,480; 3,051,690; and 3,389,087 whose disclosures areincorporated herein by reference. See also Canadian Patent No. 718,417and French Pat. No. 1,537,571.

The ashless sludge dispersants are conventionally used in lubricatingoils and are produced by condensing primary or secondary aliphaticamines, such as polyalkylene polyamines, with one or more long chain (C-C alkenyl substituted mono or dicarboxylic acids or anhydrides thereof.The alkenyl substituted dicarboxylic acid or anhydride is conventionallyprepared and the final product, before condensation with the polyamine,has a number average molecular weight generally between about 700 andabout 5,000, preferably between about 800 and about 2,000. Preferably,the alkenyl radical is derived from polyisobutylene or from apolypropylene. Alkenyl monocarboxylic acids for use in the presentinvention also will have molecular weights in the range of from about700 to about 5,000, preferably between about 800 and about 2,000. Themethods of preparation of the dicarboxylic acid materials are disclosedin U.S. Pat. No. 3,172,892, which disclosures are incorporated herein byreference.

The alkenyl monocarboxylic acids can be prepared by halogenating apolymer of a C to C mono-olefin such as polyethylene, polypropylene, orpolyisobutylene, with sufficient halogen such as chlorine to provide oneto two atoms of halogen per molecule of the olefin polymer, after whichthe halogenated polymer thus obtained is condensed with an alpha,beta-unsaturated aliphatic monocarboxylic acid of from three to eightcarbon atoms, e.g. acrylic acid, crotonic acid, methacrylic acid, etc.Thus, chlorinated polyisobutylene when reacted with acrylic acid willprovide polyisobutenyl propionic acid. This high molecular weight acidis then reacted with an aliphatic polyamine such as tetraethylenepentamine, diethylene triamine, octaethylene nonamine, or the like, toform an amide reaction product. The mole ratio of high molecular weightacid to polyamine can range from about 1:1 to about 5:1. See BritishPat. No. 1,075,121,

The sulfurized derivatives, i.e. the foregoing amino condensationproducts reacted with elemental sulfur, are described in detail in U.S.Pat. No. 3,390,086, and an alternative method of preparing suchsulfurized ashless dispersants is shown in U.S. Pat. No. 3,309,316.These patents are incorporated herein by reference. A specificdispersant which is especially useful is polyisobutenyl propionic acidcondensed with tetraethylene pentamine or polyisobutenyl succinicanhydride condensed with tetraethylene pentamine. The sulfurization ofthese materials with elemental sulfur is also disclosed in U.S. Pat. No.3,390,086.

The reaction conditions under which the monomeric or polymericolefinically unsaturated aliphatic hydrocarbons are subjected toreaction with elemental sulfur, or with sodium polysulfide, generallyinvolve the maintenance of temperatures between about 200 and about 500F., preferably between about 300 and 450 F. for a time ranging betweenabout 30 minutes and about 40 hours, preferably for between about 4 andabout 12 hours. The relative amounts of sulfur reacted with the organiccompounds may vary considerably but are generally between about 0.2 andabout 200 moles of sulfur, preferably between about 1 and about 150moles of sulfur per mole of olefinically unsaturated compound. This willresult in a final product containing a combined sulfur content ofbetween about 1.0 and about 10.0 wt. percent sulfur, preferably betweenabout 1.5 and 7.5 wt. percent sulfur. Also the reaction may be carriedout using reactants and reaction conditions shown in U.S. Pat. No.3,390,086.

The product may also be prepared using a mineral lubricating oil as areaction medium solvent or base in which the sulfurization reaction iscarried out, in which case the final product constitutes a concentrateof the sulfurized olefinically unsaturated aliphatic hydrocarbon ofbetween about 50 and about percent concentration of the sulfurizedcompound in the base oil.

This is especially useful where the reactant to be sulfurized isnormally solid but is oil-soluble also. The ashless dispersant may beadded as an oil concentrate in the lubricating oil as a base oilconcentrate of 50-70 percent active ingredient concentration.

The amount of the sulfurized olefinically unsaturated aliphatichydrocarbon which is ultimately contained in the final compounded oil,is sufficient, as a minimum, to act as an antioxidant or oxidationinhibitor and at the same time, if the unsulfurized compound possessesviscosity index improving properties, is generally sufficient, inamount, to serve also as a conventional viscosity index improver.Generally this amount will range between about 0.05 and about 10.0 wt.percent based on the oil composition, preferably between about 0.1 andabout 5.0 wt. percent, on the same basis. The ashless dispersant, and,optionally, sulfurized ashless dispersant likewise should be present insufficient amount to impart to the final oil composition recognizedbeneficial sludge dispersing properties. This generally also amounts tobetween about 0.05 and about 10.0 wt. percent, preferably between about0.1 and about 5.0 wt. percent, on the same basis as before stated.

The lubricating oils are preferably mineral lubricating oil fractionswhich are derived from naphthenic, paraffinic, aromatic, or mixed crudeoils and which are customarily employed as automotive crankcase, dieselengine, gas engine, and heavy duty or railroad diesel engine, oils.Generally, they will have a viscosity at 210 F. of between about 40 andabout SUS (Saybolt Universal Seconds) and at F. a viscosity of betweenabout and about 1,000 SUS. The viscosity indices of these oils willgenerally range between about 0 and about 100 depending upon thespecific use to which the oils are to be put. 1n the case of oilsemployed in high speed, heavy duty diesel engines, oils of highviscosity indices are often preferred, i.e. of the order of 60-100 orhigher, but usually railroad diesel engines employ lubricating oilshaving viscosities of between about 75 and about 80 SUS at 210 F. and ofbetween about 800 and about 1,250 SUS at 100 F. with viscosity indicesranging between about 55 and about 80.

The final compounded lubricating oil compositions may also contain otherconventional additives, in addition to the sulfurized viscosity indeximprovers, each in association with the ashless dispersant and,optionally, with the sulfurized ashless dispersants. These areconventional additives and they are designed to complement andsupplement the properties in the final oil which are attainable throughthe use of the two types of additives herein described and which, incombined use, show the unexpected high temperature properties. Amountssimilar to the amounts specified for the novel additives are likewiseemployed for the conventional additives such as corrosion inhibitors,(sorbitan monooleate), antioxidants, (N-phenyl alpha naphthylamine),pour point depressants, (unsulfurized wax alkylated naphthalene),viscosity index improvers (unsulfurized polyisobutylene or variouspolymethyl methacrylates, antiwear agents (the zinc salt of di((..(alkyl)dithiophosphate). detergents (the alkaline earth metal salts ofalkyl substituted phenol thioethers or sulfides), and dispersants(alkaline earth metal salts of petroleum sulfonic acids or of alkarylsulfinic acids) and the like.

A number of routine tests were carried out on compounded oils containingthe novel additives hereinbefore described on a comparative basis inorder to illustrate the beneficial effect of the combined additives.These tests may be described as follows.

The additive compositions prepared in accordance with the followingexamples were placed into various mineral lubricating oil bases and weresubjected to several types of tests in order to determine theirstability at high temperature, as well as under conventional conditions,to inhibit the formation of sludge, to determine their oxidationstability ability, their ability to disperse sludge once it is formedand in general to determine their ability to withstand severe oxidativehigh temperature conditions. Several tests include a determination oftheir bearing corrosiveness as well. One or more of the following testswere employed.

1. The Sludge Inhibition Bench Test was employed. This involved the useof a sludge-containing used oil which was rendered free of solid sludgeby centrifuging for one hour at 1,800 rpm. The supernatant oil wasdecanted from the insoluble sludge particles but the oil which was hadbeen freed of solid sludge particles did contain oil-soluble sludgeprecursors which upon heating as applied in the test would tend to formadditional oil-insoluble deposits of sludge. In a tared stainless steelcentrifuging tube, grams of supernatant used oil containing from 0.5 wt.percent to 5.0 wt. percent active ingredient to be tested was heated to300 F. for 2 hours in a constant temperature oil bath. Following theheating, the tube was cooled and then centrifuged for one hour at 1,800rpm. The supernatant oil was decanted again from the tube and anyresidual deposits of sludge were washed carefully with 99 percentn-pentane to remove all remaining oil. The weight of the solid sludgeformed in the test was determined. A blank or comparative run was alsorun in which no additive was employed in the oil. A substantial decreasein the amount of sludge deposited as compared with the amount depositedin the case of the blank run indicates that the additive had a sludgeinhibiting effect. In addition to an actual measurement, in milligrams,of the weight of the sludge so collected, a haze determination wascarried out on the centrifuged supernatant oil. This is done by means ofa nephelometer light diffraction reading. The lower the number obtained,the less haze because of the lesser number of particles present toscatter the light.

2. Another test employed in the case of some of the comparative runs isknown as the Cyclic Temperature Sludge Test. It was carried out for atotal number of hours, depending upon the particular test run, for aminimum of 105 hours and in some cases for a maximum of 168 hours. Inorder to evaluate the sludge handling ability of the additives inlubricating oil in this test, a Ford 6-cylinder engine was used whichemployed a standard carburetor. It was operated at a standard speed of1,500 rpm 1- rpm under a constant load of 140 i 2 footpounds of torque.In this test, the temperature of the oil in the crankcase was cyclicallyand sequentially raised and lowered during the period of total hours ofrunning the test. The cold phase operation, i.e. the lower temperature,was maintained for a period of 5 hours, alternated with a hot phaseoperation in which the high temperature was maintained for 2 hours. Theoil sump temperature in the cold phase was 150 F. i5 F. and the hotphase operation was 215 F. 1- 5 F. This test was used to determine theoxidation stability and the sludge inhibiting and sludge dispersingtendencies of the novel additive or additives. The base oil employed inthis test was free of other additives and would completely breakdown somuch so that it was not possible to complete the 240 hours of the run.Even after 100 hours, the top groove fill was excessive and the P.M.-lrating indicated an extremely dirty piston when using the base oilalone. Using the base oil alone, the test was not, and could not be,continued beyond 100 hours.

3. P In securing some of the following data a test known as the FalexWear Test was employed. This involves the use of a conventional FalexWear Test Machine which was operated with the test oils for 30 minutesover 500 pounds per square inch direct pressure, gauge, on a bearinghaving a rotating steel pin, which bearing was submerged in the testoil. At the end of this time, the steel pin used in the test was weighedin order to determine the amount of wear on the pin in milligrams oflost weight. This test was conducted for the purpose of measuring theamount of wear which the bearings would encounter under extremely severeconditions when operating in a bath of the test oil composition. Pinseizure or borderline pin seizure conditions are avoided, if possible,but if they do occur, the test oil is deemed to have failed in antiwearqualities.

4. Still a'further type of test was employed in some instances insecuring the data hereinafter presented. It is known as a CRC-L-38 OilOxidation Test and is designed to determine the bearing weight loss inmilligrams obtained in operating conventional standard single cylinderCLR spark ignition engines. Using the test oil, the engine was run for40 hours at a relatively high speed, i.e. 3,150 rpm at an oiltemperature of about l-200 F., with the oil sump temperature beingsomewhere between 275 and 290 F. and at high load. This test determines,inter alia, the oxidative characteristics of the oil, the copper-leadbearing weight loss, and the corrosion which the bearings undergo usingthe test oil. I

5. Still a further test involved in securing some of the following datais known as the gas engine detergency and cleanliness test. Thisinvolves the testing of compounded lubricating oils, under comparativeconditions, in a Chevrolet gas engine of 6 cylinders and of 216.5 cubicinch displacement operating on natural gas and having a horsepowerrating of 34 at 1,500 rpm. The engine operated at 2.5 percent excessoxygen in the exhaust in order to maximize nitrogen fixation and oildegradation. The test was conducted for a period of 96 hours using aparaffinic base oil containing noadditives other than those specified inthe following data. This amounted to an SAE 30- grade oil and had anoverall viscosity at 100 F. of 540 SUS and at 210 F. of 66 SUS. Theparaffinic base stock comprised 90 percent of a solvent neutral 450 SUSat 100 F. and 10 percent of a brightstock of similar characteristic witha viscosity of -160 SUS at 210 F. After running for a period of 96hours, the piston and cylinder, valves, compression grooves, rings andpiston undersides were inspected for varnish and sludge and the bearingssometimes were inspected for bearing weight loss, in milligrams. Anoverall demerit system was employed for inspection and the rating of thevarious portions of the engines was used in getting the overall meritrating. Zero rating represents a perfectly clean engine and an enginewith a 10 rating represents the dirtiest sludge and varnish depositsthat it is possible to obtain.

6. Still another test was carried out to determine the oxidationcharacteristics of the novel compounded lubricating oils. It is known asthe Lubricant Stability Test and evaluates the compounded lubricatingoils under accelerated oxidation conditions. It is a method designedprimarily to evaluate the stability of the lubricating oil compositionsunder rather severe conditions of temperature (342' F.) for a period of23 hours during which time the oil is contacted with copper-lead alloybearing materials and air is bubbled through the test oil with stirringfor this length of time. The air is bubbled in at the rate of about 2cubic feet per hour and the stirrer in the oil is rotated at about 600rpm. Fresh bearing metal specimens are inserted into the oil every 3hours. Also, viscosity in Saybolt Universal Seconds at 100 F. ismeasured and the rate of oxidation of the oil is computed on the basisof the percent increase in viscosity after 23 hours as compared to thesame oil viscosity measurement before the test is started. Bearingweight loss, in milligrams, is determined.

The following examples are illustrative of the character and nature ofthe invention but it is not intended that the invention be limitedthereto.

number average molecular weight of about 900 was reacted with 480 gramsof elemental sulfur at a temperature of about effective amounts of acommercially available overbased calcium alkaryl sulfonate and of acommercially available pour point depressant which was a 75-25 percentmixture of wax alkylated naphthalene and dilorol fumarate-vinyl acetate400 F. for 24 hours and was thereafter filtered through a filtercopolyljner' Cyclic Temperature Sludge Tests (2) were carried out as aand. The resulting product contained about 8.71 wt. percent of sulfurseries of comparative runs with all runs employing the above describedbase oil compounded as therein described. The test EXAMPLE 2 resultswere as follows: A mixture of 830 grams of the same polyisobutylene asused TABLE 11 in Example 1 together with 160 grams of elemental sulfurwas heated at 250 F. for 24 hours and filtered through a filter aid. Thefiltrate contained 2.69 wt. percent of sulfur in chemically Run I Howscombined form. No. Additive, Wt. 63 I05 147 168 EXAMPLE 3 7 10.6 wt.sulfurized A mixture of 89.7 wt. percent of polyisobutylene ofapproxipolylsilbmylcne mately the same molecular weight as thatdescribed in the 8 ig g gfi gjs g preceding examples and approximately10.3 wt. percent of WL 151135 3 A 923 elemental sulfur was heated at 400F. for 12 hours and fil- 9 10.6 wt. sulfurized tered. The filtrateproduct showed an analysis of chemically g g t g gl ggaefr A 9 94 945 68 5 6 W 0 combined sulfur of about 5.2 wt. percent sulfur. 10 Lo wt.Sulfurized 2 5 polyisobutylene plus EXAMPLE 4 10.0 wt. unsulfurized l bt l l 3.8 The same mixture as employed in Example 3 was heated at 5,:{51 2 $5 2,11 934 938 5.9 the same temperature as in Example 3 for about20 hours and filtered through a filter aid. This showed a combinedsulfur analysis of about 5.4 wt. percent.

sulfurized products of the foregoing examples were incop PlBSA/TEPA isthe conventional amide condensation ashless dispersant produced inaccordance with the teachings ofUlS. Pat No. 3,172,892. porated mto aheavy duty base lubricating oil commonly used in gas engines in varyingamounts with and without the addition of conventional ashlessdispersants and the compounded The numbers in the foregoing Table givesludge ratings oil composition was subjected to various automotivelubricawherein 10 represents a perfectly clean engine and 0 tion tests,including test (5 previously mentioned, the results represents the worstpossible dirty engine. From these data, it of which are set forth inTable l. is obvious that a beneficial synergistic sludge inhibitioneffect The base oil employed in securing the data shown in Table I isachieved through the combined use of sulfurized polyisobuwas the oilblend (SAE-3O grade), previously described, tylene and a conventionalashless dispersant (Run 9). which comprised percent of solvent neutralparaffinic base 40 A base oil blend was prepared of the same two lubeoil stock having a viscosity of 450 SUS at F. and 66 SUS at stocks inthe same weight ratios. The same additives, in the 210 F. plus 10percent of a solvent neutral brights ock same amounts, were added to theblended base except that the -160 SUS at 210 F. dithiophosphate antiwearagent was omitted and 3.8 wt. per- TABLE I Lube stability 6 test, per-Cu-Pb L-38 4 Gas Additive, cent vis. bearing 5 bearing engine 5 Run wt.increase at wt. loss, wt. loss, overall No. Additive percent 100 F.rngs. rngs. demerit l None (base oil) None 51 285 1, 000 0.63 2 Example1 5 17.7 +1.7 16 0.36 8 --{i%l i&i" I 3 0 109 06 4 Examplegkun 2 16.7+18 xam e 4. 4 6 E H 14.8 1 104 0.11

*PIBA-TEPA as used in the foregoing table is the conventional amidecondensation product of about 2.8 moles of polyisobutenyl propionic acidwith each mole of tetraethylene pentarnine.

EXAMPLE 5 About 2,000 grams of polyisobutylene having a number averagemolecular weight of about 130,000, as a 20 percent concentration in asolvent neutral 150 base lubricating oil, was

cent of the ashless dispersant PlBSA/TEPA as the acetic acid additionsalt (see US. Pat. No. 3,172,892) was added.

Comparative Falex Antiwear Tests (3) were carried out using thiscompounded base oil at 500 lbs. per square inch 65 ressure for 30minutes. The followin data wer bt d: heated with 20 grams of elementalsulfur at a temperature of p g c 0 mm about 300 F. for 8 hours. Thefinal product had a sulfur content of 1.08 wt. percent based on theweight of the polyisobutylene.

A base oil blend was prepared in the weight ratio of 9 parts of solventneutral lubricating oil stock of 100 SUS at l00 F. viscosity which-wasadmixed with each part of solvent neutral 450 SUS at 100' F. viscositylubricating oil stock. This blend also contained about 1.2 percent ofthe zinc salt of di(C C alkyl )dithiophosphate,

as an antiwear additive, and lesser but 75 12 Same as Run 11 1.2% zincdi c,-c, alkyl) dithiophosphate 5.5 13 Base oil 10.6% sulfurizedpolyisobutylene (Example 7.0

These data indicate that the product of Example 5 also exhibitssubstantial antiwear activity (Run 13) as an additional desired propertyeven though it does not appear to have superior qualities in this regardwhen compared to the use of conventional commercially available antiwearagents (Run 12).

The sulfurized polyisobutylene of Example 5 was further comparativelytested in the Sludge Inhibition Test (1) wherein a used lubricating oilcontaining sludge precursors but free of suspended sludge was employedto determine the sludge inhibiting properties of the compound. Thefollowing test results were obtained:

TABLE IV Mgs. of Sludge Run Per Grams No. Used Oil 14 Used Oil 12.0 0.4wt. PIBSA.TEPA.HAc*

Used Oil 3.5 16 Same as Run 15 1% polyisobutylene 3.4 17 Same as Run 151% sulfurized polyisobutylene (Example 5) 1.5

Prepared according to US. Patent 3,172,892.

These data illustrate the sludge inhibiting synergism in using thecombination of an ashless dispersant (PIBSA.TEPA. HAc) with sulfurizedpolyisobutylene (Run 17) in contrast to the use of the dispersant alone(Run 15) or the unsulfurized polyisobutylene (Run 16) of Example 5.

EXAMPLE 6 About 200 grams of ethylene/propylene copolymer having anumber average molecular weight of about 100,000 was treated in a lightlubricating oil serving as a solvent, with about 8 grams of elementalsulfur at a temperature of about 356 F. for 9 hours. After filtration toremove any unreacted sulfur the filtrate was found to contain 2.87 wt.percent of combined sulfur based upon the ethylene/propylene copolymerstarting reactant.

Used lubricating oil containing sludge precursors but being free ofundissolved sludge was subjected to the sludge inhibition test 1) undercomparative conditions, in which 1 percent of the starting unsulfurizedethylene/propylene copolymer was used in one instance and 1 percent ofthe sulfurized ethylene/propylene copolymer was used in the otherinstance. The unsulfurized copolymer was found to have produced 20.1milligrams of sludge per 10 grams of used oil while the sulfurizedcopolymer produced 20.3 milligrams of sludge on the same basis. However,the same two tests were repeated using the same amount of sulfurized andunsulfurized copolymer but in each case with 0.4 wt. percent ofconventional ashless dispersant being present, namely the amidecondensation product of polyisobutenyl succinic anhydride withtetraethylenepentamine. The sulfurized copolymer, in that combination,showed only 1.7 milligrams of sludge during the sludge inhibition testwhereas the unsulfurized copolymer, in such combination, showed 3.2milligrams of sludge. On a comparative basis, the same oil containing0.4 wt. percent of the ashless dispersant but no copolymer additive, ofeither type, showed a final solid sludge formation of 3.5 milligrams per10 grams of used oil.

EXAMPLE 7 A mixture of C alpha monoolefins in the amount of about 200grams was reacted with about 10 grams of sulfur at a temperature ofabout 176 F. for 12 hours. The final product contained about 4.61 wt.percent of combined sulfur. This material was subjected to the samesludge inhibition test 1) as the product of Example 6 employing a usedlubricating oil, and the same comparative tests were run including thecomparative test using the conventional ashless dispersant alonedescribed in Example 6. The results were as follows:

TABLE V Sludge, Milligrams Per 10 Grams Used Oil 1% C alpha olefins(sulfurized) 15.4 1% c alpha olefms (unsulfurized) v 15.1 1% C alphaolefins (sulfurized) plus 0.4 wt. ashless dispersant 7.0 1% C alphaolefins (unsulfurized) plus 0.4 wt. ashless dispersant 10.1 0.4 wt.ashless dispersant (alone) 9.8

Same dispersant as used in Example 6.

EXAMPLE 8 A polyisobutylene of about 300 number average molecular weightin the amount of 300 grams was reacted with 32 grams of elemental sulfurat a temperature of about 355' F. for 8 hours. After stripping theproduct with nitrogen gas for 1 hour, the product was found to containabout 5.2 wt. percent of combined sulfur.

The same used oil was employed in the sludge inhibition test (1). Theproduct of Example 8 was added to the used oil and the sludge inhibitiontest carried out. On the same comparative basis as described in the twopreceding examples, the following results were obtained:

TABLE VI EXAMPLE 9 Polyisobutylene having a number average molecularweight of about 900, in the amount of 500 grams, was reacted with 50grams of elemental sulfur at a temperature of about 482 F. for about 6hours. After stripping the reacted mixture-for about 1 hour undernitrogen gas, the product was analyzed and found to contain 3.15 percentof combined sulfur.

Used lubricating oil containing sludge precursors was used as the basetest oil for a comparative series of sludge inhibition tests (1) aspreviously described which gave the following results:

TABLE Vll Sludge, Milligrams Per Grams Used Oil l wt. polyisobutylene(reactant of Example 9 l 1.3 1 wt. sulfurized polyisobutylene (Example 9product) i 1.3 2 wt. unsulfurized polyisobutylene plus 0.4

wt. ashless dispersant" 4.5 2 wt. sulfurized polyisobutylene plus 0.4wt.

conventional ashless dispersant 0.7 0.4 wt. ashless dispersant (alone)3.4

Same dispersant as used in Examples 6-8.

From the above examples it is apparent that the combination ofsulfurized olefinically unsaturated hydrocarbons and conventionalashless dispersants has a synergistic effect on the inhibition ofoxidation inhibition of sludge formation, and a corrosion and wearprotection of sensitive bearing materials.

The Lube Stability Test (5) data illustrate the effectiveness of thesulfurized materials as oxidation inhibitors and in reducing Cu-Pbbearing corrosion. The presence of ashless dispersants does not changethis effectiveness (by itself the dispersant would provide no suchprotection), while the combination of the two types of additivesprovides a degree of engine cleanliness (gas engine test 5) that cannotbe achieved by either alone.

The L-38 Test (4) data show that the sulfurized materials provide Cu-Pbbearing protection.

The Cyclic Temperature Sludge Test (2) demonstrates the ability of thecombined additives to provide less sludge and varnish then can beobtained by either one alone. Results from this test correlate withpassenger car engine performance. Reduction of wear in the Falex Test(3) is important because of its relationship to passenger car enginewear.

The Bench Sludge Inhibition Test 1) shows synergism and is importantbecause its results correlate with the Cyclic Temperature Sludge Test(2).

What is desired to be secured by Letters Patent follows.

I claim:

1. A lubricating oil composition comprising a major proportion of amineral lubricating oil, I

a minor sludge inhibiting amount of at least one oil-soluble sulfurizedhydrocarbon produced by sulfurizing an oilsoluble olefinicallyunsaturated hydrocarbon having a number average molecular weight betweenabout 200 and about 150,000 and selected from the group consisting ofmonomeric alpha monoolefms of at least 16 carbon atoms per molecule;homopolymers of C C alpha monoolefins; copolymers of C C alphamonoolefin with a different C -C alpha monoolefin; and terpolymers of aC -C alpha monoolefin, a different C C alpha monoolefin and a thirdmonomer which is either a third and still different C --C alphamonoolefin or a C C diolefin, and a minor sludge dispersing amount of atleast one oilsoluble ashless sludge dispersant selected from the groupconsisting of condensation products of aliphatic polyamines with longchain alkenyl aliphatic monocarboxylic acids, dicarboxylic acids anddicarboxylic acid anhydrides wherein the alkenyl radical has from about40 to 250 carbon atoms.

2. A lubricating oil composition as in claim 1 wherein the amount ofsulfurized hydrocarbon and the amount of ashless sludge dispersant areeach between about 0.05 and about l0.0 wt. percent of the total oilcomposition.

3. A lubricating oil composition as in claim 1 wherein the hydrocarbonsubjected to sulfurization is at least one C,,* monomeric alphamonoolefin.

4. A lubricating oil composition as in claim 3 wherein the hydrocarbonsubjected to sulfurization is a mixture of C monoolefin monomers.

5. A lubricating oil composition as in claim 1 wherein the hydrocarbonsubjected to sulfurization is at least one homopolymer of a C -C alphamonoolefin.

6. A lubricating oil composition as in claim 5 wherein the hydrocarbonsubjected to sulfurization is a polyisobutylene.

7. A lubricating oil composition as in claim 1 wherein the hydrocarbonsubjected to sulfurization is at least one copolymer of a C C alphamonoolefin with a different C C alpha monoolefin.

8. A lubricating oil composition as in claim 7 wherein the hydrocarbonsubjected to sulfurization is a copolymer of ethylene and propylene.

9. A lubricating oil composition as in claim 1 wherein the hydrocarbonsubjected to sulfurization is at least one terpolymer of a C -C alphamonoolefin, a different C -C alpha monoolefin and a third monomer whichis either a third and still different C -C alpha monoolefin or a C -Cdiolefin.

10. A lubricating oil composition as in claim 1 which also contains aminor sludge inhibiting amount of at least one sulfurized ashlessdispersant wherein said ashless dispersant is as set forth in claim 4.

11. A lubricating oil composition as in claim 1 wherein the alkenylradical is derived from polyisobutylene.

12. A lubricating oil composition as in claim 1 wherein saidcondensation product is obtained from tetraethylene pentamine andpolyisobutenyl succinic anhydride.

13. A lubricating oil composition as in claim 1 wherein saidcondensation product is obtained from tetraethylene pentamine andpolyisobutenyl propionic acid.

2. A lubricating oil composition as in claim 1 wherein the amount ofsulfurized hydrocarbon and the amount of ashless sludge dispersant areeach between about 0.05 and about 10.0 wt. percent of the total oilcomposition.
 3. A lubricating oil composition as in claim 1 wherein thehydrocarbon subjected to sulfurization is at least one C16 monomericalpha monoolefin.
 4. A lubricating oil composition as in claim 3 whereinthe hydrocarbon subjected to sulfurization is a mixture of C20monoolefin monomers.
 5. A lubricating oil composition as in claim 1wherein the hydrocarbon subjected to sulfurization is at least onehomopolymer of a C2-C18 alpha monoolefin.
 6. A lubricating oilcomposition as in claim 5 wherein the hydrocarbon subjected tosulfurization is a polyisobutylene.
 7. A lubricating oil composition asin claim 1 wherein the hydrocarbon subjected to sulfurization is atleast one copolymer of a C2-C18 alpha monoolefin with a different C3-C18alpha monoolefin.
 8. A lubricating oil composition as in claim 7 whereinthe hydrocarbon subjected to sulfurization is a copolymer of ethyleneand propylene.
 9. A lubricating oil composition as in claim 1 whereinthe hydrocarbon subjected to sulfurization is at least one terpolymer ofa C2-C18 alpha monoolefin, a different C3-C18 alpha monoolefin and athird monomer which is either a third and still different C3-C18 alphamonoolefin or a C4-C18 diolefin.
 10. A lubricating oil composition as inclaim 1 which also contains a minor sludge inhibiting amount of at leastone sulfurized ashless dispersant wherein said ashless dispersant is asset forth in claim
 4. 11. A lubricating oil composition as in claim 1wherein the alkenyl radical is derived from polyisobutylene.
 12. Alubricating oil composition as in claim 1 wherein said condensationproduct is obtained from tetraethylene pentamine and polyisobutenylsuccinic anhydride.
 13. A lubricating oil composition as in claim 1wherein said condensation product is obtained from tetraethylenepentamine and polyisobutenyl propionic acid.